Package delivery companies pick up millions of packages daily from thousands of locations over a large geographical area and transport them to sorting facilities, primarily by truck and airplane, so they can be routed to a correspondingly large number of scattered destinations. To meet a rigorous schedule and provide accurate deliveries, a package delivery company must use automated transfer systems in the sorting facilities to match incoming packages with proper outgoing transport headed for the packages' destinations. Because deliveries are time sensitive, the sorting equipment must be very fast, yet provide gentle and accurate handling of packages.
Belt and roller conveyor systems have often been used in package sorting systems to move packages from incoming loading docks to outgoing transport. A initial sorting of packages traveling along a conveyor may be accomplished by diverting packages from the conveyor based on their destinations, or based on their size or another characteristic.
To automate handling of articles traveling on conveyor systems, conveyor diverter assemblies of various types have been developed. Roller bed diverters using right angle transfer belts are shown in U.S. Pat. Nos. 4,798,275, and 4,174,774. However, these diverter systems divert articles at right angles to the primary conveyor direction of travel. Therefore, a fast moving article must slow down so that the transfer belts may frictionally the article for the radical right angle change of direction. If the article is traveling at high speed, it may slide uncontrolled through the diverter and miss its intended path. Thus, this system sacrifices production speed for accuracy.
Other diverter systems have been developed to divert the articles diagonally from the main conveyor. U.S. Pat. No. 5,551,543 shows a sorter with angled rollers for this purpose. In one embodiment, the articles are either carried straight through on chains, or lowered onto diverting idler rollers while being pushed. In another version, steerable idler rollers guide the articles either straight or off to the side. In another version, the angled idler rollers are shifted up into contact with the articles. In a final version, there are two sets of idler wheels arranged at different angles, one of which is vertically movable. At any particular output location along the main conveyor path, the articles can only be diverted to one side of the path.
U.S. Pat. No. 3,608,713, has a main conveyor consisting of angled, powered rollers mounted to travel with a chain drive. If a parcel is to move straight with the conveyor, the rollers do not rotate. If the parcel is to be diverted, the powered rollers are activated to divert the parcel without slowing the chain drive. The apparatus only diverts in the direction the rollers are angled, and requires a complex mechanism to carry all the rollers with the chain conveyor.
U.S. Pat. No. 3,926,298, provides a main conveyor having multiple powered wheels, and a diagonal belt conveyor fitted between the wheels below the normal conveyor surface. A section of the drive rollers can be lowered to drop a parcel onto the belt conveyor, without interrupting the speed of articles moving along the primary path. However, the belt conveyor can divert in only one direction.
It is also known to provide slanted barriers over a moving conveyor to guide articles off the conveyor. These barriers may be stationary or may swing out over the conveyor to divert an article. In some such prior systems, the swinging diverters carry moving belts to assist in moving the article laterally, as shown in U.S. Pat. Nos. 1,729,671, 4,711,357, and 4,364,465. However, unless there are two swinging barriers, one swinging from each side of the conveyor, or one barrier pivoted at the center of the conveyor (severely limiting the size of articles that can pass it), the known slanted barriers cannot divert articles selectively off both sides of the conveyor at the same diverting location. Furthermore, prior systems cannot adjust the angle of the barrier while having it direct the article to exit at the same spot along the conveyor.
Other prior systems push articles off conveyors with pushing arms that sweep directly across the conveyors. Examples of such systems are shown in U.S. Pat. Nos. 3,026,988, 4,295,559, and 4,732,260. These systems either cannot turn a package as it is pushed off the conveyor, or require a complex articulating mechanism to move an article engaging member with the article.
U.S. Pat. No. 5,027,939 discloses a sorting conveyor in which the main conveyor is a bed of cross tubes carried by chains attached to either side of the tubes. A line of pusher units slide freely between adjacent pairs of the tubes under the guidance of cross-over tracks at each diverting location. A mechanism engages rollers extending down from the pusher units, which travel with the tubes, and guides them to the cross-over tracks when an article is to be pushed off the conveyor. The disadvantage of this system is that the pushers move both forward with the conveyor and across the conveyor, requiring a more complex conveyor mechanism. In addition, if a single pusher in the line becomes jammed at the entrance to the cross-over location, the entire conveyor may go down until a complex repair is performed.
U.S. Pat. No. 4,633,996 discloses a diagonal interceptor including an endless flexible member recessed slightly below the surface of a main conveyor, which is routed down and under the interceptor. The endless flexible member carries diverter plates that can be elevated to a position in which they deflect articles passing on the conveyor. This system requires a mechanism for raising and lowering the diverter plates.
Thus, there is a need in the art for a diverter that possesses greater flexibility in the manner and direction in which it discharges articles from a conveyor, does not travel with the conveyor, and is easy to repair.